The synthesis and spectroscopic properties of a series of boron-free meso-aryl-substituted [14]triphyrin(2.1.1) compounds containing either peripheral bicyclo[2.2.2]octadiene (BCOD) (2a−c) or benzene rings (3a−c) (aryl = phenyl a, 4-fluorophenyl b, and 4-methylbenzoatephenyl c) are reported. These compounds represent the first examples of free-base contracted porphyrinoids with 14 π-electron aromatic systems containing only the standard pyrrole and isoindoline moieties of the porphyrins and tetrabenzoporphyrins.

A novel alpha-diketone precursor of pentacene, 6,13-dihydro-6,13-ethanopentacene-15,16-dione, was prepared and converted successfully to pentacene in 74 % yield by photolysis of the precursor in toluene: Irradiation of the diketone solution in toluene with light of 460 nm under an Ar atmosphere caused the solution to change from yellow to fluorescent orange-pink within a few minutes, after which, purple precipitates appeared. After 35 min, the solution changed to colorless and the purple precipitates were filtered to give pentacene in 74 % yield. By contrast, in the presence of oxygen, the color of the solution changed from yellow to pale yellow, and only 6,13-endoperoxide of pentacene was quantitatively obtained. The rate of the reaction upon photolysis was measured by observing the decay of n-pi* absorption of the precursor at 460 nm, and was found to be similar in both the presence and absence of oxygen. Therefore, the photoreaction of the alpha-diketone precursor seemed to occur via the singlet excited state. Because the T-T absorption of pentacene was observed upon photolysis of the precursor in the nanosecond transient absorption measurement under an Ar atmosphere, the excited triplet state of the pentacene generated singlet oxygen by sensitization, and it reacted with the ground-state pentacene to give the 6,13-endoperoxide. The alpha-diketone deposited on glass was also converted successfully to pentacene film by photoirradiation. In addition, diketone precursors of a mixture of 2,8- and 2,9-dibromopentacene and 2,6-trianthrylene were also prepared and their photoconversion was performed.

The metal-free and meso-free [14]triphyrin(2.1.1) compound was successfully prepared based on the intramolecular McMurry coupling reaction of diformyl-tripyrrane in 16% yield, and was converted to the bowl-shaped Mn(I)(TriP)(CO)(3) and Re(I)(TriP)(CO)(3).